1. Field of the Invention
This invention relates to the field of apparatus and methods for imparting torsion to tubular members. More particularly, it relates to apparatus and methods for rotating, spinning, or applying torque to tubular members such as pipe, collars, tubing, and casing.
2. Description of Prior Art
Applicant is aware of the following prior art which is deemed material to the examination of this application and which is the closest prior art of which the applicant is aware: U.S. Pat. No. 3,892,140; U.S. Pat. No. 3,906,820; and Houston Engineers H-E Multi Grip Breakout Chain Tong described in the 1974 edition of the composite Catalogue of Oil Field Equipment & Service, Volume 2, at page 2697. The rotary drive apparatus of U.S. Pat. No. 3,892,140 is a mechanical casing tong in which rotational torque is applied to a cylinder by means of a tensioned, motor-driven chain and a series of rollers. The subject matter of U.S. Pat. No. 3,906,820 ('820) is an apparatus and method for mechanically spinning pipe used in oil wells. The '820 apparatus also employs a motor-driven chain and a series of rollers. The Houston Engineers chain tong is a typical example of the many prior art tongs. It is a manually operated breakout tool comprising a lever arm, a chain, and a pivotable body. None of the above-mentioned prior art apparatuses claims or suggests the adjustability features of the present invention which assure maximum positive load reaction at specified positions and which teach a method of reacting the load directly through the thickness of the chain.